Can printing or decorating machines, especially high speed continuous can printing machines, operate by the impingement of a rotating, image-carrying blanket wheel and an oppositely rotating can carrying mandrel wheel assembly. The blanket wheel comprises an endless blanket which is at least as wide as the length of the cans being printed. The blanket carries a series of wet ink images circumferentially spaced on its resilient periphery. The mandrel wheel assembly comprises a mandrel wheel mounted with a series of circumferentially spaced, rotatable mandrel spindles over which cans are fitted. The cans rotate on the mandrel wheel into registry and contact with the images on the surface of the blanket wheel. Each mandrel spindle generally includes structure for removing cans from or drawing cans onto the mandrel spindle.
During high speed printing, a can will occasionally fail to properly seat on a mandrel spindle or a gap will occur in the continuous can infeed to the machine causing one or more mandrel spindles not to have a can received thereon. In such circumstances, it is necessary that the mandrel spindle not be moved into contact with the blanket wheel to prevent the mandrel spindle surface from being printed. A number of different mechanisms have been utilized in the past to provide such a "skip-print" feature, such as U.S. Pat. Nos. 3,665,583 to Hartmeister et al.; 4,037,530 to Sirvet and 4,498,387 to Stirbis, all of which are incorporated herein by reference thereto.
In apparatus accomplishing the "skip-print" feature, it is highly desirable to locate the sensing apparatus as close as possible to the intended point of contact with the printing blanket wheel means. As the speed of the processing system is greatly increased, the time for response to the sensing apparatus to move the mandrel spindle and any cylindrical container thereon away from the printing path is greatly reduced. In prior art devices, it has been necessary to limit the speed of the processing system or to move the sensing apparatus further away from the point of contact of the cylindrical container with the printing wheel blanket means in order to move the mandrel spindle out of the printing path.